As a Brazilian, some things:
Development in Brazil is usually done in Cheap. Freelancing is mostly done through Networking and pay is short. If you get a job at a bigger company, maybe you have a shot at earning more, and I can refer you to good places, but usually it’s intense, at least 40 hours a week, and the pay is not really great, especially when considering US companies paying for remote Jobs.
If you still want to work with a brazilian company, you have a startup ecossystem in the three southernmost states (Better pay, better flexibility), lots of big, rigid companies in São Paulo (Some with better pay, some with more flexibility, usually not the same ones), and a lot of opportunities pretty much everywhere else (Small businesses, freelancing, pr agencies and even some startups etc., usually lots of hard work for low pay, with very rigid structures, or freelancing DIY).
As for Argentina, do not work for an Argentinian company. The country is in a pinch, and it’s looking awfully bad right now. Earn from somewhere else and it will be a breeze, get you pay in their currency and you may find yourself in financial trouble pretty soon.